Effect of exogenous taurine on growth, oxidative defense, and nickel (Ni) uptake in canola (Brassica napus L.) under Ni stress

Nickel (Ni) contamination and its associated hazardous effects on human health and plant growth are ironclad. However, the potential remedial effects of taurine (TAU) on Ni-induced stress in plants remain obscure. Therefore, the present study was undertaken to examine the effect of TAU seed priming (100 and 150 mg L ‒1 ) as an alleviative strategy to circumvent the phytotoxic effects of Ni (150 mg kg ‒1 ) on two canola cultivars (Ni-tolerant cv. Shiralee and Ni-sensitive cv. Dunkeld). Our results manifested an apparent decline in growth, biomass, photosynthetic pigments, leaf relative water content, DPPH free radical scavenging activity, total soluble proteins, nitrate reductase activity, and nutrient acquisition (N, P, K, Ca) under Ni toxicity. Further, Ni toxicity led to a substantial increase in oxidative stress reflected as higher levels of superoxide radicals (O 2 •‒ ) and hydrogen peroxide (H 2 O 2 ) alongside increased relative membrane permeability, lipoxygenase (LOX) activity, and Ni accumulation in leaves and roots. However, TAU protected canola plants from Ni-induced oxidative damage through the amplification of hydrogen sulfide (H 2 S) production that intensified the antioxidant system to avert O 2 •‒ , H 2 O 2, and malondialdehyde (MDA) production. Further, TAU-mediated increase in H 2 S levels maintained membrane integrity that might have improved ionomics and bettered plant growth under Ni toxicity.